1. Field of the Invention
The invention relates in general to a displaying method, and more particularly to a displaying method for a transflective type display device.
2. Description of the Related Art
With the rapid advancement of technology of liquid crystal display (LCD), the features of LCD such as luminance and resolution have become a focus for LCD manufacturers.
RGBW type display device is different from any other ordinary conventional RGB type LCD in that a transparent filter element is added to the existing color filter for forming a white sub-pixel. The white sub-pixel does not need additional filter material. Therefore, RGBW type LCD has higher transmission and better luminance. In recent years, both the transflective type and the reflective type RGBW type LCD have made remarkable progress. The two types of LCDs consume less power than the conventional display device, and have become mainstream LCD products.
However, when a white sub-pixel (W) is added to the original RGB pixel array, under the same distribution area of the pixels, the pixel area which originally has three three-color sub-pixels (RGB) is now has four RGBW sub-pixels, causing the aperture ratio of the pixel to decrease. Furthermore, with the increase of the white sub-pixel, a corresponding driving line for the white sub-pixel also needs to be added, causing the amount of driving lines to increase by one third of the original amount and incurring more manufacturing cost.
Under the above conditions, a modified pixel array having the same RGBW sub-pixel is provided to resolve the above problems of having a decreased aperture ratio but an increased amount of driving lines. Referring to FIG. 1A, an illustrative diagram of an improved conventional strip type pixel array is shown. As indicated in FIG. 1A, a modified strip white (MSW) type pixel array 1 includes several rows of red sub-pixels (R), green sub-pixels (G), blue sub-pixels (B), and white sub-pixels (W), wherein every consecutively connected three sub-pixels in each row form a square. Besides, two sub-pixels having the same color disposed in two neighboring rows are alternated by two sub-pixels along the arrangement direction of the pixel array. When the MSW pixel array 1 is used in a transflective type LCD, a white sub-pixel is used to display in the reflective mode. The display device with the MSW type pixel array has the transflective effect by two ways to display an image no matter the LCD is in the transmissive mode or the reflective mode. The first, a transflective board having particular light transmission rate is disposed in the white sub-pixel for allowing the backlight to penetrate through and the external light to be reflected, wherein the transmission rate is determined according to the needs of the design. The second, a reflective board having a certain ratio to the aperture of the white sub-pixel is disposed in the white sub-pixel for allowing the backlight to penetrate through and the external light to be reflected.
In the transmissive mode, the backlight is turned on and a sub-pixel rendering (SPR) method is employed to drive the sub-pixels of the MSW pixel array 1. Let the driving of the pixel unit of FIG. 1A be taken for example. Presume that the pixel unit 10 marked by bold lines is selected. When the pixel unit 10 is driven, an image data having three-color sub-pixel (RGB) values is converted into the data format of four-color sub-pixel (RGBW) values. As the pixel unit 10 lacks the white sub-pixel (W), the white sub-pixels (W) nearest to the pixel unit 10 will be driven according to the weighted value obtained through calculation to compensate the color. When the backlight is turned on, the sub-pixels of the MSW pixel array 1 driven by the sub-pixel rendering (SPR) method is capable of maintaining the resolution of the original image without adding any extra driving lines.
However, when the trans-flective type display device with the MSW type pixel array 1 is in the reflective mode (the backlight is turned off), only the white sub-pixel (W) has a reflective area, the above driving method will result in image defects. Referring to FIG. 1B, an illustrative diagram of the pixel array of FIG. 1A when the backlight is turned off is shown. As indicated in FIG. 1B, when the backlight is turned off, only the white sub-pixel (W) is able to display an image. Compared with FIG. 1A, the selected pixel unit 10 including only three-color sub-pixels (RGB) will be dark, and other pixel units including three-color sub-pixels (RGB) will be dark either. Thus, the image cannot be clearly displayed if the sub-pixel rendering (SPR) driving method is used in the reflective mode. If image processing is not performed in advance, the display device will show a zigzag image. For example, presume that the displayed image contains a text, if the dark pixel units are located at the edge of the text. Therefore, the text with zigzag edge in the image will be shown, largely reducing the display quality.